In its pictured use, the pigtail is plugged into a MacBook, and the USB-C charger cable is plugged into the adapter and the wall charger.

Can I use this the other way around? ie, the pigtail plugs into the wall charger, and the long single cable goes to a MacBook?

I ask because I would like to have the charger, a USB hard drive, and a large TV all sitting together. The ideal would be that only the 2m USB-C charger cable goes from that collection of peripherals to my MacBook.

Ran a system report with the USB-C Digital AV Multiport Adapter attached and it shows up under a USB 2 Hub attached to the USB-3 bus. The speed for the adapter is listed at 1.5 Mb/sec while the speed listed for the USB-3 hubs is listed at 5 Gb/sec.